In the machining of workpieces on machine tools, the workpieces must be aligned with respect to the coordinates of the machine tool before the machining operation and before they are clamped on the clamping surface of the machine tool table. The T slots of the machine tool table extend along one of these coordinates, generally in the direction of sliding of the machine tool table, or, if this is stationary, in one of the directions of movement of the tool. Accordingly, the T slots can serve for exact alignment of the workpiece. To this end, abutment pieces in the form of fitting pieces are known which fit exactly into the narrow section of the T slot, which is referred to hereinafter as the leg section. The width of this leg section is generally termed the slot width. The thickness of the fitting pieces must correspond precisely to the slot width, so that the fitting pieces may be able to engage in the leg section of the slot without any play. Introduction of the fitting pieces into the T slot is difficult and time consuming, since they must fit into the leg section of the T slot with a very close tolerance and must therefore be driven into the T slot with a hammer from the end face of the table. In this process there is a danger of damaging the T slot and also the fitting piece, because the two parts may bind against one another. Moreover, there are various standardized slot widths, so that fitting pieces of corresponding thickness must be available for each slot width. Finally, there is also the disadvantage that fitting pieces which engage too loosely in the T slot may slip during the alignment of the workpiece and also not form a precise abutment, since their abutment surface is not exactly in alignment with the lateral surface of the leg section of the T slot.
The problem underlying the invention is to provide an abutment piece adapted to be inserted in a T slot of a machine tool table which is suitable for a plurality of slot widths, can be inserted in the T slot rapidly and without any risk of damage and can be clamped therein free from play.
According to the invention, this is achieved in that the abutment piece has a head portion projecting beyond the clamping surface and the width of which is greater than the slot width of the leg section, has a neck portion engaging in the T slot and the width of which is smaller than the slot width, the head portion has on its side facing away from the abutment surface a bearing surface inclined at 45.degree. with respect to the abutment surface and extending toward the neck portion and by means of which the head portion is supported on the chamfered outer edge of a lateral surface of the leg section, the said outer edge adjoining the clamping surface, and on the neck portion of the abutment piece there is provided a wedge element movable parallel to the abutment surface and perpendicularly to the head portion by means of a clamping screw and engaging in the widened flange section of the T slot, the wedge surface of the said wedge element, which faces the bearing surface and is inclined at an opposite angle with respect to the abutment surface, being pressable against the inner edge of the corresponding lateral surface of the leg section.
Due to this conformation, the novel abutment piece is suitable for a plurality of different slot widths. With the clamping screw slackened, it can be introduced into the slot without any effort from the end face of the machine tool table, there being a clearance between the abutment piece and the surfaces and edges of the T slot cooperating with it. Damage to the abutment piece or even to the T slot is impossible during this operation. When the clamping screw has been tightened, the abutment piece is clamped free from play in the desired position in the T slot. When this happens, the abutment surface of the abutment piece is applied free from play against a lateral surface of the leg section of the T slot. On the opposite side of the leg section of the T slot, the head portion of the abutment piece is supported by its bearing surface on the chamfer of the outer edge of the lateral surface, while the wedge surface of the wedge element is pressed against the inner edge of this lateral surface. The abutment surface of the abutment piece is exactly aligned with the lateral surface of the leg section of the T slot, so that the abutment piece is aligned precisely with respect to the T slot and can consequently also serve as a precise abutment or stop for the workpiece.
Further advantageous developments are characterized in the subclaims.